A mulling process is an easy process for manufacturing powder. Various mulling processes have been developed since ancient times. Powder manufacturing in the chemical industry, mining industry, and so on, has the purpose of enhancing a subsequent process efficiency using a large specific surface area of powder, mixing it with another material, or separating and recovering a useful component in a rock, rather than the purpose of obtaining powder itself. The mulling process is also applied to a living body.
Notwithstanding a long history, a mulling process has characteristics of a unit operation in that it requires consumption of a great amount of energy, and efficiency thereof is considerably low. Further, research into mulling has been considerably delayed compared to other research fields. Meanwhile, since a particle diameter distribution considerably affects development of new materials, a mulling process for achieving a desired grain distribution will become more important in the future.
As generally known, a solid body has cohesion energy. If the solid body is mulled and then a new surface is generated, the cohesion energy is converted to surface energy.
If the newly generated surface area is increased as mulling progresses, the surface energy is also increased. Then, if both become equal, the mulling process no longer progresses, thereby reaching the mulling limit.
Change of various physical properties due to such a mulling process is utilized in several fields.
That is, there are advantages, such as surface area increase, reactivity improvement, density increase, thermal capacity decrease, resolution improvement, viscosity change, adhesion force increase, reaction rate improvement, thinning, and so on, in chemistry and metal fields.
Further, there are advantages, such as transparency increase, gloss improvement, smoothness improvement, dry velocity improvement, freshness improvement, osmosis into fiber, and so on, in the pigment and cosmetics fields.
Further, there are advantages, such as surface area increase, treatment for being fit to drink, precipitation decrease, mixability improvement, uniformity of particle diameter, absorptiveness improvement, osmosis improvement, and so on, in the food and medicine fields.
According to usages of ultra fine particles having these advantages, they are variously used in new material fields such as ceramics, superconductors, and so on, the chemical field for petrochemicals, pigments, paint, resins, toner, and so on, the medicine field for cosmetics, injectable solutions, sugars, proteins, and so on, and the food field for calcium, vitamins, enzymes, food additives, and so on.
Various mullers have been developed due to the above stated advantages of the usages of the ultra fine particles.
Such a mulling process is a unit operation for obtaining fine particles by finely mulling solid material via mechanical methods. That is, the mulling process is one of the ancient unit operations in flour milling, pigment manufacturing, ore processing, and so on. Various kinds of mullers are known, and improvement of the muller has long been required.
Mullers may be generally classified according to particle size (mainly, product particle). That is, according to particle size, mulling may be broadly classified into crushing (several tens of an to between 10 and 19 cm), intermediate crushing (several cm to several tens of m m), comminuting (several cm to between 10 and 19 m m), and fine comminuting (several mm to several m m). Further, mullers may be classified by a power transmission mechanism (for example, reciprocating, rotary, link, and so on), and an actuating system (for example, compression, vibration, and so on).
Compression Type
A jaw crusher crushes a rock positioned between a fixed disc and a movable disc using a strong compression force. The crushing characteristics are different depending on whether an upper disc is the movable disc (in the input direction of a raw material) or a lower disc is the movable disc (in the output direction of a product). The jaw crusher is widely used as a first crusher. A gyratory crusher also conducts crushing by compression force. However, the gyratory crusher bites and crushes a rock by eccentrically rotating an inverted inner cone. The gyratory crusher requires a small quantity of raw material, having a higher continuity, and easily controls particle size compared to the jaw crusher. In a cone crusher, the inner cone is not eccentrically rotated. The cone crusher bites and crushes a material by rotation, and obtains a finer particle size.
High Velocity Rotation Type
A hammer crusher crushes a raw material by cutting, shearing, and collision by rotating a cutter or a hammer at a high velocity. Hammer crushers are widely used. The hammer crusher covers a considerably small mulling area by repeating a collision repulsion using a repulsion plate mounted to an inner wall of the crusher. Further, the hammer crusher conducts some classification by mounting a screen or a grid at a lower part of the crusher.
Among known crushers, there are jaw crushers, cone crushers, hammer crushers, cutter mills, shredders, hammer mills, roll crushers, edger runners, stamp mills, disc mills, pin mills, and so on.
Further, mulled material to be processed is recovered through particle size classification based on particle characteristics and particle diameter. Among known classification methods, there are wind power classification and hydraulic classification. Classifiers have also been variously devised.
However, according to the prior mullers, there have been problems in that pulverization is limited, system efficiency is low compared to input energy for pulverization, and productivity is lower since cleaning of the system is difficult.
Further, there have been defects in that increase of equipment and decrease of productivity both occur since pulverized material to be processed should be separated through a separate classifier.